I would still sign up for the airline's frequent flyer program before booking. Sometimes, when it comes to involuntary bumping or other things, being a member (even with 0 miles in the account) may be better than being a non-member.

Also, on CX, it is easier to view and manage your itinerary on-line if you associate it with an existing frequent flyer account at the time of booking.

If you are thinking of using BART ( http://www.bart.gov ) to get from the airport to San Francisco or other places, be aware that the union contracts end soon and there may be a strike or lockout. BART is also nowhere near as clean as Hong Kong MTR subway trains.